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330                        QREO&ON AND MJSSOREO&ON                      CHAP.
Xiyliodon was a hornless creature, but with only two toes, the
two lateral digits being represented by the merest rudiments of
metacarpals. The other metacarpals were unusually long.
Ampfaimeryx (also called 2£iphodontotherium) is much more
imperfectly known, but belongs to this family or to that of the
Oaenotheriidae. Dichodon is another member of the same family.
fsan, Oreodontldae.—This family, consisting of numerous
genera, is limited to the North American continent. Its range
in time is from the Eocene to the Lower Pliocene. The family
as a whole is to be distinguished by a number of primitive
characters. The dentition is complete; the feet are four- or
even five-toed ; the orbit is sometimes open behind. The canines
of the lower jaw are not more pronounced than the incisors.
The characteristics of the group will be further developed by
a consideration of some of the principal genera which are in-
cluded in this family.
Oreodon is a Miocene form about as large as a Peccary. The
skull has a short face with a completely-closed orbital cavity.
In front of the orbit is a deep pit, not a mere deficiency of
ossification, such as occurs in many Artiodactyles. This is
placed on fche lachrymal bone, and is in fact a lachrymal fossa,
such as occurs in other forms. The odontoid process of the axis
vertebra is somewhat cheese-taster shaped, as in recent Artio-
dacfeyles« There are fourteen dorsal vertebrae and a very large
number of caudals. The radius and the ulna are completely
separated, as are the carpals. There are five digits to the fore-
limbs. The fibula is complete and independent. The hind-foot
is four-toed. Several species of the genus are known.
Merycochoerus is an allied Miocene genus. It is more
massive in form than the last, but otherwise does not present
differences of importance.
Jfesoreodon is another genus of this family which presents
some curious features of organisation. In the skull and teeth
there is nothing very noteworthy, but the hyoid is remarkable.
This appendage of the skull is by no means always preserved,
and when it is, it might be denied that it belonged to any
particular sknlL In the present case there appears to be no doubt
as to the identity of the bones, which resemble the corresponding
bonoB of the Perifisodactyla much more than they do those of
•otter Aiilodaefcylea Associated with the bones an ossified